By discussion[1], someday we will remove rw_page function. If so, we need something to detect such super-fast storage which synchronous IO operation like current rw_page is always win. This patch introduces BDI_CAP_SYNCHRONOUS_IO to indicate such devices. With it, we could use various optimization techniques. [1] lkml.kernel.org/r/<20170728165604.10455-1-ross.zwisler@xxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> --- drivers/block/brd.c | 2 ++ drivers/block/zram/zram_drv.c | 2 +- drivers/nvdimm/btt.c | 3 +++ drivers/nvdimm/pmem.c | 2 ++ include/linux/backing-dev.h | 8 ++++++++ 5 files changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/block/brd.c b/drivers/block/brd.c index bbd0d186cfc0..1fdb736aa882 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -20,6 +20,7 @@ #include <linux/radix-tree.h> #include <linux/fs.h> #include <linux/slab.h> +#include <linux/backing-dev.h> #ifdef CONFIG_BLK_DEV_RAM_DAX #include <linux/pfn_t.h> #include <linux/dax.h> @@ -449,6 +450,7 @@ static struct brd_device *brd_alloc(int i) disk->flags = GENHD_FL_EXT_DEVT; sprintf(disk->disk_name, "ram%d", i); set_capacity(disk, rd_size * 2); + disk->queue->backing_dev_info->capabilities |= BDI_CAP_SYNCHRONOUS_IO; #ifdef CONFIG_BLK_DEV_RAM_DAX queue_flag_set_unlocked(QUEUE_FLAG_DAX, brd->brd_queue); diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 98ef1a8389b0..23172641fc01 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1556,7 +1556,7 @@ static int zram_add(void) blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX); zram->disk->queue->backing_dev_info->capabilities |= - BDI_CAP_STABLE_WRITES; + (BDI_CAP_STABLE_WRITES | BDI_CAP_SYNCHRONOUS_IO); add_disk(zram->disk); ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj, diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c index d5612bd1cc81..e949e3302af4 100644 --- a/drivers/nvdimm/btt.c +++ b/drivers/nvdimm/btt.c @@ -23,6 +23,7 @@ #include <linux/ndctl.h> #include <linux/fs.h> #include <linux/nd.h> +#include <linux/backing-dev.h> #include "btt.h" #include "nd.h" @@ -1402,6 +1403,8 @@ static int btt_blk_init(struct btt *btt) btt->btt_disk->private_data = btt; btt->btt_disk->queue = btt->btt_queue; btt->btt_disk->flags = GENHD_FL_EXT_DEVT; + btt->btt_disk->queue->backing_dev_info->capabilities |= + BDI_CAP_SYNCHRONOUS_IO; blk_queue_make_request(btt->btt_queue, btt_make_request); blk_queue_logical_block_size(btt->btt_queue, btt->sector_size); diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index 39dfd7affa31..7fbc5c5dc8e1 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -31,6 +31,7 @@ #include <linux/uio.h> #include <linux/dax.h> #include <linux/nd.h> +#include <linux/backing-dev.h> #include "pmem.h" #include "pfn.h" #include "nd.h" @@ -394,6 +395,7 @@ static int pmem_attach_disk(struct device *dev, disk->fops = &pmem_fops; disk->queue = q; disk->flags = GENHD_FL_EXT_DEVT; + disk->queue->backing_dev_info->capabilities |= BDI_CAP_SYNCHRONOUS_IO; nvdimm_namespace_disk_name(ndns, disk->disk_name); set_capacity(disk, (pmem->size - pmem->pfn_pad - pmem->data_offset) / 512); diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index 854e1bdd0b2a..cd41617c6594 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -123,6 +123,8 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); * BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold. * * BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback. + * BDI_CAP_SYNCHRONOUS_IO: Device is so fast that asynchronous IO would be + * inefficient. */ #define BDI_CAP_NO_ACCT_DIRTY 0x00000001 #define BDI_CAP_NO_WRITEBACK 0x00000002 @@ -130,6 +132,7 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); #define BDI_CAP_STABLE_WRITES 0x00000008 #define BDI_CAP_STRICTLIMIT 0x00000010 #define BDI_CAP_CGROUP_WRITEBACK 0x00000020 +#define BDI_CAP_SYNCHRONOUS_IO 0x00000040 #define BDI_CAP_NO_ACCT_AND_WRITEBACK \ (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB) @@ -177,6 +180,11 @@ long wait_iff_congested(struct pglist_data *pgdat, int sync, long timeout); int pdflush_proc_obsolete(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos); +static inline bool bdi_cap_synchronous_io(struct backing_dev_info *bdi) +{ + return bdi->capabilities & BDI_CAP_SYNCHRONOUS_IO; +} + static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi) { return bdi->capabilities & BDI_CAP_STABLE_WRITES; -- 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>